Types of muntin bar: stick-on, between panes, structural and duplex

Muntin bars can transform a facade more effectively than a new render colour. The difficulty starts with the choice, because one name covers four quite different solutions: structural, stick-on, between-the-panes and duplex. They differ in price, appearance, cleaning and in whether they can still be fitted to a window already in the wall. In this guide we compare all four and show how to choose the width and colour of the profile so the division of the glass looks natural.

What a muntin bar is and where it came from

A muntin bar is a strip that divides the area of a window into smaller panes. Originally it was purely structural: early glassworks could not make large sheets, so a window was assembled from many small panes set in a timber or lead frame. When the technology advanced the division stayed, now in a decorative role. Today it is chosen for style, not necessity.

That original purpose explains why muntin bars look so right on buildings that draw on tradition, and can be awkward on a modern form with large glazing. A division always makes a window look smaller and gives it character - sometimes that is the aim, sometimes not.

Four kinds of muntin bar

Structural muntin bars

The solution closest to the original. The window really is divided into separate panes, each holding its own sealed unit. The effect is unquestionably the most faithful, because the division shows in daylight and in every reflection.

The price, though, is the highest of all the options, and the construction has more unit edges, which tells on the thermal performance of the whole window. Then there is cleaning: every pane has to be done separately. This type is ordered while the window is being made and cannot be added later.

Stick-on bars, also called Viennese

Stick-on bars are profiles fitted to the surface of the glass on both sides, usually with adhesive tape. In the full version they are completed by a spacer in the profile colour set inside the unit, so the division looks as if it ran through the whole thickness of the glass.

This is the most often chosen option, and it is not hard to see why. It gives a crisp, three-dimensional division with a real shadow, costs a fraction of structural bars and, above all, can be fitted to a window already in the wall. Cleaning needs a little care at the profile edges, but the glass itself remains a single sheet.

Between-the-panes bars

Also called internal bars. These are thin strips, usually aluminium, sealed inside the glazing unit. The glass stays smooth on both sides, so cleaning is trivially easy and nothing can damage the division.

The drawback is the look: the profile is flat and casts no shadow, so close up it reads more like a print than a structure. Bear in mind too that they are fitted at the glass works, while the unit is being made. Changing your mind afterwards means replacing the whole pane.

Duplex bars

Duplex combines the two previous solutions: a bar inside the unit plus stick-on profiles on both faces of the glass, aligned exactly with it. The result comes very close to a structural bar while keeping a single sheet of glass.

This is the option for jobs where the detail matters, in period-style houses and buildings under conservation guidance. It costs more than a stick-on bar alone, but still far less than a structural division.

The four types compared

Criterion	Structural	Stick-on	Between panes	Duplex
Fidelity of appearance	highest	high	moderate	very high
Shadow effect	yes	yes	no	yes
Cost	highest	low	medium	medium
Fitting to an existing window	no	yes	no	no
Ease of cleaning	low	medium	highest	medium
Replacement years later	replace the window	replace the profile	replace the glass	replace the glass

If the windows are already in, the table comes down to one row: realistically only stick-on bars are on the table. The other three call for a decision when ordering the windows, or for replacing the glazing unit.

Choosing the width and bevel of the profile

We make stick-on bars in several series that differ in section and therefore in the character of the shadow they cast on the glass. Widths run from 18 mm to 75 mm.

Series	Sizes	Bevel
ASG 13	27×13, 34×13, 45×13, 65×13 mm	15 degrees
ASG 9	27×9, 34×9, 45×9, 65×9 mm	15 degrees
SD	30×9, 36×9, 48×9, 36×12, 48×12 mm	30 degrees
SG 15	27×10, 33×10, 45×10, 75×10 mm	15 degrees
SG 25	27×13, 34×13, 44×13 mm	25 degrees
G 8	20×13, 25×13, 45×13, 75×13 mm	8 degrees
G 45	18×10, 27×13, 35×13 mm	45 degrees
Flat	23×13, 22×10, 26×10 mm	no bevel

Two simple rules help with the choice. First, the width is matched to the size of the window: 18-27 mm profiles suit small sashes and dense divisions, 34-48 mm is the all-purpose range, and 65-75 mm is reserved for large glazing, where a narrow bar simply disappears. Second, the bevel decides how pronounced the shadow is: the steeper it is, the more sharply the profile stands away from the glass.

We supply the bars in 5 m lengths, which allows pieces to be cut without excess waste even on unusual divisions.

Colours and seals

Two base colours are standard: white RAL 9016 and cream RAL 9001. For coloured and wood-effect windows we wrap the profiles in Renolit, Hornschuch, Cova and LG foils, so a bar can be matched to anthracite as readily as to golden oak or walnut.

A separate decision is the seal that closes the joint between profile and glass. There is black, grey RAL 7001 and light grey RAL 7035. A dark seal emphasises the line of the division and deepens the effect; a light one stays discreet. On white windows grey is usually chosen, as black can be too much of a contrast.

Setting out the division

The commonest mistake is a division invented without reference to the proportions of the window. A few pointers that save the result:

• Panes should be close to square or to an upright rectangle. Narrow horizontal strips look accidental.
• Keep the same division across the whole facade. Windows of different sizes may have different numbers of panes, but the panes themselves should stay comparable.
• Remember the view from inside. A bar also cuts across what you look at from the room, so avoid running a line at eye level on a window with a view.
• Draw the division before ordering. A simple sketch with dimensions lets you count the metres and avoid corrections once the profiles are stuck on.

A detailed step-by-step account of fitting, including preparing the glass and the temperature requirements, is in our complete guide to stick-on muntin bars.

Not only on windows

Stick-on profiles increasingly turn up beyond window joinery. They divide the glazing of internal and patio doors, cabinet and display fronts, sliding wardrobe doors, and even large mirrors, which start to look like windows once a division is added. The fitting principle stays the same: a clean, degreased surface and even pressure on the profile.

On such work narrower profiles are usually chosen, in the 18-27 mm range, because the panes are smaller than on a window.

Frequently asked questions

Stick-on or between-the-panes? If appearance and the shadow effect matter to you, choose stick-on. If easy cleaning and completely smooth glass come first, between-the-panes bars are better. Stick-on bars have one more advantage: you can fit them to the window you already have.

Do muntin bars worsen a window’s thermal performance? Stick-on bars do not touch the glazing unit, so they do not change its figures. Between-the-panes bars sit inside the unit, and structural bars divide the window into separate panes, which means more edges in the construction as a whole.

Are Viennese bars the same as stick-on bars? Yes, the terms are used interchangeably for profiles fitted to the surface of the glass.

Can they be removed if you tire of them? Stick-on profiles come off along with the tape, and any adhesive residue is removed with a glass cleaner. The other kinds mean replacing the glass or the whole window.

How wide should bars be on a large window? On large glazing, reach for 65-75 mm profiles. A narrow bar is lost on a big sheet and the division stops reading from a distance.

Do muntin bars suit anthracite windows? Yes. We wrap the profiles in foils of the same shades the windows are made in, so the division merges with the frame.

In summary

Choosing the type of muntin bar starts with one question: are you still ordering the windows, or do you already have them? In the first case the full palette is open, from between-the-panes to structural. In the second, stick-on bars are the practical choice - and they happen to offer the best ratio of effect to cost, changing the character of a whole facade without touching the windows.

At the TECHNOLOG wholesale we make stick-on muntin bars in eight profile series, widths from 18 to 75 mm, in standard colours and foil wrapped. Send us the window dimensions and the division you have in mind and we will work out the metres and prepare a quote. Get in touch and we will recommend the profile that suits your joinery.